1. Field of the Invention
This disclosure generally relates to the field of iontophoresis, and more particularly to the delivery of active agents such as therapeutic agents or drugs to a biological interface under the influence of electromotive force and/or current.
2. Description of the Related Art
Iontophoresis employs an electromotive force and/or current to transfer an active agent such as an ionic drug or other therapeutic agent to a biological interface, for example skin or mucus membrane.
Iontophoresis devices typically include an active electrode assembly and a counter electrode assembly, each coupled to opposite poles or terminals of a voltage source, for example a chemical battery. Each electrode assembly typically includes a respective electrode element to apply an electromotive force and/or current. Such electrode elements often comprise a sacrificial element or compound, for example silver or silver chloride.
The active agent may be either cation or anion, and the voltage source can be configured to apply the appropriate voltage polarity based on the polarity of the active agent. Iontophoresis may be advantageously used to enhance or control the delivery rate of the active agent. As discussed in U.S. Pat. No. 5,395,310, the active agent may be stored in a reservoir such as a cavity, or stored in a porous structure or as a gel. In further development of iontophoresis devices, an ion selective membrane may be positioned to serve as a polarity selective barrier between the active agent reservoir and the biological interface, as discussed in U.S. Pat. No. 5,395,310. The membrane, typically only permeable with respect to one particular type of ions, i.e., that of a charged active agent, prevents the back flux of the oppositely charged ions from the skin or mucous membrane.
Stability of the active agent stored in an iontophoresis device is an important factor in assessing the commercial acceptance of iontophoresis devices. Some active agents, including drugs, cannot maintain their chemical integrity or efficacy over long period of time in solution phase. An iontophoresis device that addresses this factor is desirable.